The developing endosperm tissue of the maize kernel represents an excellent system to study the molecular biology of the coordination and timing of the activity of families of genes. The synthesis of zein, the major storage protein in maize endosperm tissue protein bodies, involves the coordinated activity of a complex multigene family of some 100 genes. This multigene family can be divided into at least four subfamilies of genes and their corresponding mRNAs and proteins on the basis of the relatedness of their nucleotide and amino acid sequences. In addition, the protein bodies contain small subfamilies of zein associated proteins (ZAPs). These various groups of protein body proteins differ in the timing of their expression and their response to various mutations affecting endosperm development. Recent results indicate tht some of the genes in a subfamily are clustered in a limited region of the genome. This proposal has three objectives: first, to determine the organization of genomic regions which contain zein and a ZAP subfamily gene cluster; second, to study the transient expression of cloned zein and ZAP genes (and their structural modifications) after introduction into maize protoplasts derived from (normal and mutant) endosperm and other plant tissues; and third, to attempt to introduce cloned zein genes into heterologous plants (and possibly maize) and study the structural features of the genes that control their developmental expression in plant seeds.